Bags that easily collapse under a small exterior force into a shape determined by the applied force because they are constructed of flexible material for most of their surface have many short-comings. Various bellows designs in present use for collapsible bottles provide containers that collapse, but tend to spring back or expand to resume their original shape. Latching mechanisms or over-center features to overcome this phenomenon have been used to provide a container that changes its shape and size from one useful configuration to the other.
Containers that collapse in a telescoping manner that depend on the draft of the sides to ease the collapsing stress are severely limited in geometries that are functional. Additionally, these containers are usually capable of other than axial collapsing or telescoping, which may be undesirable. For example, see U.S. Pat. No. 2,880,902 which teaches a collapsible article, such as a drinking cup, of the bellows type. The device has a generally conical body made from a relatively flexible material such as polyethylene. The body has a plurality of annular stepped sections of successively decreasing diameter, alternate ones of which have relatively thick walls while the other ones have relatively thin walls.
Of interest is U.S. Pat. No. 2,723,779 which describes a tubular plastic container having thin sidewalls with spiral ridges around the outside of the wall. The spiral ridges aided the collapse of the walls onto the axis of the container thereby dispensing viscous materials, such as cake frosting. While such a container reduces its volume as it is emptied, since it collapses along its axis, its axial length or height remains approximately the same. Additionally, it appears unlikely that this container would retain its contracted shape without an applied outside force thereon.
In an improvement to the container of U.S. Pat. No. 2,723,779, U.S. Pat. No. 2,899,110 to the same inventor describes two bellows-type collapsible containers. One has a plurality of straight, parallel pleats normal or transverse to the axis of the container, while the other has a plurality of spiral pleats, similar to the '799 design. These versions not only collapse in volume, but also in their axial direction. However, each of these containers are of complex design and are not readily adaptable to conventional container configurations. They also appear to be limited to circular cross-sections.
Collapsible containers employing conventional bellows designs are well known. U.S. Pat. No. 3,587,937 discloses a collapsing dispenser of the bellows type having a spout that projects outward and retracts with the contents of the container. U.S. Pat. No. 4,044,836 describes an axial compression powder dispenser of the bellows type, in particular for dispensing fire extinguishing powders. Finally, U.S. Pat. No. 4,492,313 teaches a foldable plastic bottle of circular bellows-like configuration. The bellows are formed to over center as the bottle is collapsed thus preventing the bottle from returning to its full height before or after the cap is placed upon the bottle. The bellows have conical sections comprising alternating short portions and long portions, the short portions being at greater angle to the bottle axis than the long portions.
While a latching feature such as that described in the '313 patent may be desirable in some applications, other applications may utilize a configuration that can be collapsed and expanded many times. The bottle type of the '313 patent only collapses to more than half of its original size, and thus may not collapse to the extent desired or required by some applications.